When comparing MacVim vs Divvy, the Slant community recommends MacVim for most people. In the question“What are the best power user tools for macOS?”MacVim is ranked 18th while Divvy is ranked 19th. The most important reason people chose MacVim is:

OS X input methods

Pro

Extensive community support

Pro

Automatic font substitution

In cases of a selected font missing certain characters, MacVim will find a font that has that character.

Pro

Vimtutor teaches the basics of Vim in 30 minutes

Vimtutor is an excellent interactive tutorial for people with no prior experience of Vim. It's bundled with Vim and takes about 30 minutes to complete.

Pro

Everything is a mnemonic

Vim associates keys with words. For example, d is for "delete" and w is for "word". To perform an action you string together letters. Thus, to delete a word, press dw.

This way it's possible to abstract a large amount of functionality that Vim provides in an intuitive way.

Pro

Enables effective keyboard-driven editing due to its modal nature

Interaction with Vim is centered around several modes. Each mode has a different purpose and switching between them changes behaviour and keybindings. There are 12 modes in total (six basic modes and six variations on basic modes) and four of them are used commonly.

Insert mode is for entering text. This mode most resembles traditional text entry in most editors.

Normal mode (the default) is entered by hitting ESC and converts all keybindings to center around movement within the file, search, pane selection, etc.

Command mode is entered by hitting ":" in Normal mode and allows you to execute Vim commands and scripts similar in fashion to a shell.

Visual mode is for selecting lines, blocks, and characters of code.

Modes allow separating concerns between various tasks and reusing keys for different kinds of functionality. As a result, the workflow becomes more efficient.

Pro

Multi-byte support

Permits writing characters that don't fit in one byte, most notably logograms (for writing in languages such as Japanese, Chinese, and Korean) and Unicode characters.

Pro

Requires virtually no configuration & is very easy to use

Divvy uses a drop and drag style UI that's simple to use and doesn't require any setup or configuration to get started.

Pro

Reasonably configurable

You can change the grid dimensions and a very other visual settings to suit your needs.

Pro

Has keyboard shortcuts

Although it's not in the same level as something like bug.n, Divvy does support the use of keyboard shortcuts to move windows about. You can even create custom shortcuts.

Cons

Con

Slow when opening files with very long lines

A lot of very long lines can make MacVim take up to a minute to open, where a few other editors take only a few seconds to load the same file.

Con

Difficult learning curve

MacVim after all is still Vim, and with that comes the complexity that Vim brings and the difficult learning curve that needs to be overcome.